178 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



A young lobster about six weeks old, raised from the egg, and probably in the 

 sixth stage, was light brownish-olive on the upper surface, the chehe being more 

 decidedly brown. The under surface of the body was almost colorless. The usual 

 cream-colored or white spots occurred on the carapace and appendages and the ter- 

 minal spines of the abdominal pleura were whitish. The large claws, which show no 

 special differentiation, are held together in frout of the auimal as it swims forward. 

 When suddenly disturbed, the young lobster opens its claws, spreads wide its arm- 

 like chelipeds, at the same time raising itself into a threatening attitude, ready to 

 receive or strike a blow. The iridescent pigment of the eyes is no longer visible. 

 Some measurements of parts of this lobster are as follows: 



Measurements. 



Millime- 

 ters. 



Len gth 16 



Length of thorax, including rostrum 



Greatest width of thorax j 4 



Length of antennary flagellum ! 11 



Length of propodas of large chela 5. 5 



Lobsters in the fifth stage, which are raised in aquaria, swim less at the surface 

 than in preceding stages, going frequently to the bottom of the jars for their food, and it 

 is during this and partly in the sixth stage that the pelagic life of the lobster comes 

 to an end. It then sinks to the bottom and leads an entirely new life. Its larval 

 characters have completely disappeared, and buds of the modified appendages of the 

 first abdominal segment have begun to grow out. In locomotion and general habits it 

 resembles the adult animal closely, but t lie final adult condition is only attained after 

 a long series of molts, which require, in all probability, from four to five years. 



The sixth stage lasted (in three cases observed) 9, 14, and 18 days, respectively. 



SEVENTH STAGE. 



The seventh stage can not be distinguished by any known characteristics from 

 that which immediately precedes and follows. Unless one has watched and recorded 

 the molts, it is impossible to say at this or a later period through just how many 

 ecdyses the animal has actually passed. The larval stages merge insensibly into 

 those of the adolescent period, and these pass as gradually into those of the adult, so 

 it will be more profitable to follow the history of individual lobsters from this period 

 onward rather than to attempt to describe stages which have no marked distinguishing- 

 characters. 



In table 34 I have recorded the molts of thirty-nine youug lobsters raised during 

 the summers of 1891 and 1892. The increase at each ecdysis and the increase percent 

 (that is, the ratio between the actual increase and the former length) are also given. 

 Many of the adolescent lobsters, which it should be understood are the remnant of a 

 much larger number which I attempted to raise, died shortly after the last recorded 

 molt. Some, however, were living when I was obliged to leave Woods Hole, at the 

 middle or latter part of August, and doubtless could have been reared had they 

 received the necessary care. The life-history, as illustrated in table 34, has been 

 followed from the time of hatching to the tenth stage or ecdysis, when the animal 

 is over an inch long and about three months old. 



We have considered in detail at the close of Chapter in the bearings of these 

 observations upon the rate of growth in the lobster. 



